The present disclosure relates to a contact temperature probe for measuring a temperature of a semiconductor substrate.
During the manufacture of semiconductor devices, a substrate is frequently exposed to elevated temperatures during processing. Examples of such processes include plasma ashing of photoresist, chemical vapor deposition, annealing, and the like. Some of these processes include an ion source, which introduces an ion flux to the substrate surface during processing. It is generally desirable to monitor the temperature during these and other processes since temperature often impacts the quality and success of the process. Moreover, the measurement equipment used for monitoring the temperature should provide accurate and reproducible readings with minimal or no delay.
Contact temperature measurement is one such technique that is often used to monitor the temperature of the semiconductor substrate during processing. Contact temperature measurement techniques typically include contacting the substrate with a probe containing a temperature sensor. The probe is typically fabricated from materials that possess high thermal conductivity, such as aluminum. Many of the advances in contact measurement are directed to improving the accuracy of the temperature readings as well as the response times.
In U.S. Pat. No. 5,791,782 to Wooten et al. and U.S. Pat. No. 6,332,709 to Burke et al., contact temperature measurement probes are disclosed having a probe head which pivots under the weight of a semiconductor substrate so as to maintain close contact therewith. The pivoting probe head reduces contact resistance between the substrate and the probe head resulting in greater accuracy in the temperature measurements. Thermally isolating temperature sensor wires extending from the probe head provides further improvements.
In the methods and apparatus described in these and other patents, accurate temperature measurements can be obtained in a variety of processing environments. However, it has been determined that inaccuracies in the temperature measurement can occur in processing environments that include an ion source. Semiconductor manufacturing processes that include an ion source have a propensity to charge the substrate during processing. That is, ions can contact the substrate and form a low voltage potential in the substrate. Contact temperature measurement probes fabricated from thermally conductive metals such as aluminum, although suitable for providing sufficient thermal conductivity, are also electrically conductive. As a result, the low voltage potential formed in the substrate by the ions is recorded by the temperature sensor creating a bias in the displayed temperature readings. Thus, these methods and apparatus may not be suitable for semiconductor manufacturing processes that include an ion flux to the substrate surface and require accurate monitoring of the temperature.
Disclosed herein is an apparatus and process for measuring a temperature of a substrate in a processing environment. In one embodiment, a contact measurement probe in accordance with the present disclosure comprises a probe head having a contact surface made of a ceramic material for contacting a substrate; and a temperature sensor having lead wires which exit the probe head and run through a shield for shielding the wires from the process environment, wherein the probe head is supported only by the temperature sensor lead wires and the shield does not touch the probe head. Preferably, the ceramic material is selected from the group consisting of AlN, BeO, and combinations comprising at least one of the foregoing ceramic materials.
In another embodiment, the contact measurement probe comprises a probe head comprising a unitary monolith of a ceramic material and a temperature sensor in thermal communication with the probe head. The temperature sensor comprises lead wires that run through a shield for shielding the wires from the process environment, wherein the probe head is supported only by the temperature sensor lead wires and the shield does not touch the probe head.
In another embodiment, a probe head for the contact temperature probe comprises an electrically conductive pad; and a ceramic material or polymeric material disposed on a contact surface of the pad, wherein the ceramic material is selected from the group consisting of AlN, BeO, and combinations comprising at least one of the foregoing ceramic materials, and wherein the polymeric material is selected from the group consisting of polyimides, and polyetheretherketones.
In another embodiment, a contact temperature probe comprises a probe head made of a ceramic or polymeric material having an electrical resistivity greater than or equal to about 1xc3x97106 ohm-cm and a thermal conductivity greater than or equal to about 100 W/m-K at 100xc2x0 C.; and a temperature sensor in contact with the probe head having lead wires that run through a shield for shielding the wires from the process environment, wherein the probe head is supported only by the temperature sensor lead wires and the shield does not touch the probe head.
A contact temperature measurement process for eliminating electrical bias in a process environment that includes an ion source comprises contacting a substrate with a contact measurement probe comprising a probe head and a temperature sensor, wherein the probe head comprises a flat contact surface made of a ceramic material, wherein the temperature sensor has lead wires which exit the probe head and run through a shield for shielding the wires from the process environment, and wherein the probe head is supported only by the temperature sensor lead wire and the shield does not touch the probe head; generating a thermoelectric voltage in the temperature sensor as a function of temperature, wherein the thermoelectric voltage is free from electrical bias; and converting the thermoelectric voltage to an actual temperature of the semiconductor substrate.
The above described and other features are exemplified by the following figures and detailed description.